/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/DynamicMeshOctree3.h
Call TriangleFunc for all triangles in the octree "above" the CutSet (ie at tree cells that are not children of any cut cells)
void CollectRootTriangles ( const [FTreeCutSet](API\Runtime\GeometryCore\DynamicMesh\FDynamicMeshOctree3\FTreeCutSet) & CutSet, [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< void(int)> TriangleFunc ) const